Pressure-relief device



C. C. EGBERT.

PRESSURE RELIEF DEVICE.

APPLICATHIN FILED JULY 23,1120. 7

Patented Oct. 18, 1921.

A TTORNEY UNITED STATES CHARLES C. EGBERT, OF NIAGARA FALLS, NEW YORK.

PRESSURE-RELIEF DEVICE.

Application filed July 23,

T 0 Mi whom it may concern:

Be it known that I, CHARLES C. Eennn'r, a citizen of the United States of America, and a resident of the cit of Niagara Falls, county of Niagara, and tate of New York, have invented certain new and useful Improvements in Pressure-Relief Devices, of which the following is a full, clear, and exact description.

My invention relates generally to safety devices, in the nature of bursting plugs, used to relieve the pressure within any receptacle and adapted particularly for use in connection with penstocks.

As is well known to those skilled in the art, the bursting plugs or plates used at present have a very small factor of safety. For example, assuming the normal pressure is three hundred fifty pounds per square inch and that it is desired to have the plug or plate burst at four hundred fifty pounds, this would mean that there would be a factor of safety of 450/350 or only 1.29. Assuming the ordinary surge in the penstock increases the pressure fifty pounds or to four hundred pounds per square inch, this only allows a factor of safety of 1.12. The result is that such ordinary surges will eventully weaken the fastenings of the plate or the bolts thereof and cause them to frequently burst with the attending loss of service, and the expense and annoyance in replacing the broken parts.

Furthermore, the usual factor of safety, first above given, is so small that if the surge should be in excess of fifty pounds the plate is very likely to burst before the actual pressure, at which it is set, has been reached.

The principal object of my invention has been to provide a device which shall overcome the objections above set forth,and one in which it shall be possible to make the factor of safety large enough so that the device shall in no wise .become weakened by the ordinary surges which occur in turbine penstocks.

Another object has been to provide a device of this nature having a nozzle which, when the cap at the end thereof has been blown off, will project the water in a well defined stream, so that it maybe confined and discharged in a manner which will not cause injury by the impact or erosive action of the stream.

Another object has been to provide a device in which a sensitive relief valve may be employed in connection with an auxiliary Specification of Letters Patent. I

Patented Oct. 18, 1921. 1920. Serial No. 398,524.

P1813011, whereby a well defined and easily controlled percentage of increase in pressure of the water within the penstock may be transferred to the auxiliary piston, and cause the safety plug to be blown.

Another object has been to provide a device in which the parts broken at each rupture shall be reduced to a minimum.

The above objects and advantages have been accomplished by the device shown in the accompanying drawings, of which:

Flgure 1 is a longitudinal, sectional view of my complete device, showing it attached to a penstock.

F 1g. 2 is an enlarged fragmentary view of the same with slight modifications.

In the drawings, 5 represents the penstock in which water under pressure is conducted to a turbine. While I have shown and will descrlbe my invention'in connection with a turbine pens'tock, it is obvious that the device is applicable to any receptacle carrying pressure. The penstock 5 is provided with a branch connection 6, to the flange 7 of which is bolted the nozzle 8 of my device. The outer end of the nozzle 8 is preferably provided with a counterbore 9 in which is fitted the bursting plug 10. The bursting plug is provided with an outwardly projecting flange 11. A plurality of bolts 12 are screw-threaded into the outer end of the nozzle 8, each having a head 13, by which the bolt-may be screwed into the nozzle or removed therefrom when ruptured. The heads 13 of these bolts lie preferably within a recess 14, provided between the end face of the nozzle and the inner face of the flange 11 of the bursting plug. The bolts 12 are extended outwardly and pass through apertures 15 formed in the flange 11 of the plug 10, and each is provided with a nut 16, whereby the bursting plug is securely held in position. Each of the bolts 12 has a peripherally reduced portion 17, thereby giving each bolt a breaking area which causes the bolt to rupture when subjected to the strain of a definite number of pounds and at a predetermined point in its length.

Surrounding the mouth of the nozzle 8 is a cylinder flange 18, in which an annular cylinder 19 is provided. This cylinder opens toward the flange of the bursting plug 10 and within it is slidably mounted an annular piston 20. The inner diameter of the annular piston 20 is somewhat less-than the outer diameter of the flange 11. of the burst ing plug 10, so that the flange overhangs the piston 20. The parts are so designed that the face of the piston is in contact withthe inner face of the flange 11 when the parts are in their normal position as shownin the drawings.

Near the outer end of the cylinder, an annular groove 22 is provided. This groove is arranged some distance from the outer face of the annular piston at its outer periphery and within the groove is arranged a retaining ring 23. This retaining ring 23 projects above the groove and into the cylinder 19, in which position it is held by a plurality of bolts 24. This retaining ring 7 not, therefore, be described in this specification, except to, state that it is of atype which will operate within a very small ercentage' of a predetermined pressure. onnecting the inlet flange 31 of the relief valve with the flange 29 is a pipe 32 and cormecting the outlet flange 33 of therelief valve with the flange 27 is a pipe 34. By this arrangement the ports 26 and 28 are connected with each other through the relief valve 30. 35 is a bypass pipe which has a valve 36 connected therein and by which fluid may be allowed to pass from pipe 32 to pipe 34 without passing through the relief valve. By this means, the pipe 34, port 26 and the annular recess 25 may be filled with fluid, so that when the valve 30 responds to .a predetermined increase in pressure, the piston 25 will be immediately acted upon'in the least possible interval of time. This may be accomplished by providing a small lea-kage hole in the relief valve 30, but I prefer to employ the controlled by-pass pipe 35 for thispurpose. A drip pipe 37 is provided on the pipe 34 and prevents any possible leakage through the relief valve 30 or the bypass pipe 35 from building up pressure within the pipe 34, port 26 or annular recess 25. This drip pipe is made large enough so as to prevent the leakage referred to, but not so large as to materially reduce the pressure in the recess 25 when the relief valve 20 operates,

The annular piston 20 in the face contacting with the flanget'll of the bursting plug is formed with a plurality of relief grooves 38 (Fig.2), whereby any leakage of pressure past the joint between the bursting plug 10 and the nozzle 8 will be prevented from passing between the piston and cylinder or building up pressure within the annular reunnecessary. The bursting plug 10 may also be similarly packed.

From' the foregoing description, it will be understood that when the pressure of the fluid within the penstock 5 rises'to the predetermined amount, at which the relief valve 30 is set, therelief valve will operate and allow fluid to pass through port 28, pipe 32, pipe 34, port 26 and to the annular cham ber 25,]where its pressure-will be exerted against the bottom ofthe annular piston20. This pressure together with that exerted against the bursting plug 10 will rupture the bolts 12 and blowithe bursting pluglO out of the end of the nozzle 8, thus relieving the abnormal pressure within the penstock 5, .and projecting the fluid passing through the nozzle in a well defined stream. The replacement of the bursting plug will, of course, require that the waterfrom the nozzle 8. be shut off, either by shutting off the penstock 5 or by closing a shut-off valve placed be'tween'the nozzle 8 and the branch 6 of thepenstock. The broken bolts 12 may then be removed and replaced by new ones and the same or .a new bursting plug put back in position.

By proportioning the area of the annular piston 20 with respect to the area of the relief cover'lO, the bolts 12 may be reduced at. 17 to an area at which they will burst under the combined pressures on the annular nular'recess 25 and the annular piston 20 for exerting pressure. against the flange 11 of the bursting plug, it is obvious that I may use aoplura-lity of cylinders arranged about the nozzle8 and each having a piston bearing against the flange 11. Instead of the retaining. ring 23 fltting into the annular groove in thecylinder, it is clear that a flange may be bolted onto the 'faceof the cylinder or a plurality of bolts passing through. the cylinder may be used to limit the motion of the piston 20. .These and other modifications of the details herein shown and described may be made without departing from the spirit of my invention or the scope of the appended claims, and I do not, therefore, wish to be limited-to the exact embodiment herein shown and described, the form described being merely a preferred embodiment thereof.

Having thus described my invention, what I claim is:

1. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized by having a bursting plug exposed to the fluid pressure within the receptacle, fastening means for the plug, having a relatively high factor of safety, and means for exerting an auxiliary pressure against the plug and the fastening means.

2. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized by having a bursting plug exposed to the fluid pressure within the receptacle, fastening means for the plug, having a relatively high factor of safety, means for exerting an auxiliary pressure against the plug and the fastening means, and a pressure relief valve for controlling the auxiliary pressure.

8. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized by having a bursting plug exposed to the fluid pressure within the receptacle, fastening means for the plug, having a relatively high factor of shfety, auxiliary means for transmitting pressure to the plug, a pressure relief valve, and means connecting the receptacle with the relief valve and the auxiliary means.

a. The combination with a receptacle containing fluid under pressure, of a pressure reliefdevice characterized by having a bursting plug exposed to the fluid pressure within the receptacle, fastening means for the plug, having a relatively high factor of safety, a cylinder located on the pressure side of the plug, a piston slidably mounted in the cylinder and normally bearing against the plug, and means, connected with the receptacle, for exerting a pressure against the piston.

5. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized by having a nozzle, a bursting plug covering the nozzle outlet and exposed to the fluid pressure within the receptacle, an annular cylinder surrounding the nozzle outlet, a piston slidably mounted in the cylinder and bearing against the plug, and means, connected with the receptacle, for exerting a pressure against the piston.

6. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized by having a nozzle, a bursting plug'covering the nozzle outlet and exposed to the fluid pressure within the receptacle, an annular cylinder surrounding the nozzle outlet, a piston slidably mounted in thecylinder and bearing against the plug, a pressure relief valve, and means connecting the receptacle with the pressure relief valve and the annular cylinder.

7. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized by having a nozzle, a bursting plug covering the nozzle outlet and exposed to the fluid pressure within the receptacle, an annular cylinder surrounding the nozzle outlet, a piston slidably mounted in the cylinder and bearing against the plug, means carried by the cylinder for limiting the movement of the piston, and means, connected with the receptacle, for exerting a pressure against the piston.

8. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized by having a nozzle, a bursting plug covering the nozzle outlet and exposed to the fluid pressure within the receptacle, the plug being provided with a lateral flange forming a recess between it and the end of the nozzle, fastening means for the plug, passing through the recess, a piston normally bearing against the flange, the piston bein provided with relief grooves in the face which contacts with the flange, and means, connected with the receptacle, for exerting pressure against the piston.

9. The combination with a receptacle containing fluid under pr ssure, of a pressure relief device characterized by having a nozzle, a bursting plug covering the nozzle outlet and exposed to the fluid pressure within the receptacle, an annular cylinder surrounding the nozzle outlet, a piston slidably mounted in the cylinder and bearing against the plug, the cylinder being formed with an annular recess at its bottom, and means connectin the receptacle with the recess for exerting a pressure against the piston.

10. The combination with a receptacle containing fluid under pressure of a pressure relief device characterized by having a nozzle, having a counterbore at its outer end, a bursting plug fitted into the counterbore and exposed to the fluid pressure within the receptacle, an annular cylinder surrounding the nozzle outlet, a piston slidably mounted in the cylinder and bearing against the plug, and means, connected with the receptacle, for exerting pressure against the piston.

11. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized by having a nozzle, a bursting plug covering the nozzle outlet and exposed to the fluid pres sure within the receptacle, an annular cylinder surrounding the nozzle outlet, a piston slidably mounted in'the cylinder and bearing against the plug, a pressure relief valve, means connecting the receptacle with the relief valve and the annular cylinder, and avalve-controlled by-pass for conducting the fluid around the relief valve.

12. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized by having a nozzle, a bursting plug covering the nozzle outlet and exposed to the fluid pressure within the receptacle, an annular cylinder surrounding the nozzle outlet, a

piston slidably mounted in the cylinderand bearing against the plug a pressure relief valve, conduits connecting the receptacle with the relief valve and the annular cylinder, and a drip pipe attached to the conduit connecting the relief valve with the cylinder.

13. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized byhaving a bursting plug exposed to the fluid pressure Within the receptacle, fastening means for the-plug, and means for exerting an auxiliary pressure against the plug and the fastening means. 7

14. The combination with a receptacle containing fluid under pressure, of a pressure relief device characterized '7 by having a bursting plug exposed to the fluid pressure within the receptacle, fastening means for the plug, a cylinder located on the pressure side of the plug, a piston slidably mounted in the cylinder and normally bearing against the plug, and means, connected with the receptacle, for exerting a pressure againstthe piston.

In Witness whereof I have hereunto signed my name.

CHARLES c. EGBERT. 

